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Occasional Contributor
Posts: 13
Registered: ‎11-03-2016
Accepted Solution

18-135 Sharpness

[ Edited ]

I've had this lens for a while, using it on my 650D, and I'm not loving the results.  I'm finding that at almost all focal lengths, the edges are just plain blurry.  I know that few lenses are sharp throughout the frame, and I don't expect "L" quality but what I'm seeing doesn't seem acceptable.  Yes, you get what you pay for, but even my old 28-80 USM was better than this 18-135.  (Sometimes I wish I would have kept the 28, even though it's not really wide enough for a crop body.)

 

The middle of the frame consistently is very sharp. I've tried stopping down (usually to no more than f/8) turning the IS on and off, and try my best to avoid camera shake. My shutter speed rarely is less than my focal length. Could my AF method have something to do with it? I usually stay on AI Servo.  I've tried manual focusing, but with the Rebel's smaller viewfinder, it's not easy and all of the times that I've tried MF, the results have been equally disappointing.  

 

Could I have just gotten a bad copy?  Decentering issue?  Or is something that I'm doing wrong?

 

 

 

DPP_0079.JPG

 

 

 

DPP_0079.JPGUntitled01a.JPG

Occasional Contributor
Posts: 13
Registered: ‎11-03-2016

Re: 18-135 Sharpness

I forgot to mention, in case it's not apparent, that the third pic is a 100% crop of the right side.  

Esteemed Contributor
Posts: 4,191
Registered: ‎08-13-2015

Re: 18-135 Sharpness


GenXRailmedia wrote:

I forgot to mention, in case it's not apparent, that the third pic is a 100% crop of the right side.  


I don't think you need to use AI Servo for this type of shot.  One Shot mode should have been good enough.  Your shutter speed seems to have been high enough to freeze the train.  I suppose it was not moving at a cruising speed.    

 

http://www.dofmaster.com/doftable.html

 

What would you estimate the distance between the camera and the train to be?  According to the chart at the above link, you could be seeing the far edge of your DOF.  I wish your crop were a little larger, to include some of the dome in the background.  

 

If you say all shots are blurry around the edges, then I will take your word for it.  But, I suspect this particular shot is close to the edge of your DOF, or your hyperfocal distance.  It's hard to tell.  I'm comparing stuff to the left to the engine, to that to the right of the engine.

 

Try taking shooting in One Shot mode, both with and without IS active.

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Reputable Contributor
Posts: 598
Registered: ‎11-14-2012

Re: 18-135 Sharpness

[ Edited ]

You can use Live view and the focus box. Live view is slower but hasn´t any AF variance issues. Focus at something in the edges and upload a new picture.

I also have a question for you. Where did you get your camera, because your firmware version is 5.5.9. It feels like a service firmware. Do you have a factory menu?

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Honored Contributor
Posts: 7,284
Registered: ‎12-07-2012

Re: 18-135 Sharpness

I don't think there is anything wrong with the lens.  It is what it is.

I may point out, you took the worst part (right edge and behind) of your shot for IQ and enlarged it to pixel level.  Also an extreme condition.

 

Switch your shooting mode to One Shot.  There are few, very few, reasons to use AI-Servo certainly not this one.

 

The only way you can confirm the IQ of a lens is with a test target and a dedicated series of tests..

A lot of Canon stuff. Along with, a lot of other stuff.
Respected Contributor
Posts: 1,513
Registered: ‎02-17-2016

Re: 18-135 Sharpness

Here is a site that gives a testing methodology and some test charts:

http://www.bobatkins.com/photography/technical/testing_lenses.html

Occasional Contributor
Posts: 13
Registered: ‎11-03-2016

Re: 18-135 Sharpness

[ Edited ]

Waddizzle wrote:

 What would you estimate the distance between the camera and the train to be?  According to the chart at the above link, you could be seeing the far edge of your DOF.  I wish your crop were a little larger, to include some of the dome in the background.  

 

Wadizzle, I  can post another crop if you think it may help.  I would estimate that I was about 100 feet from the train, which was traveling 23-25 MPH, for what it's worth.  

 

For a while, I was using AI Servo for some sports work, and it seemed to work for moving trains, especially ones that were head-on shots where the the train was coming straight at me.  Maybe it works better in different situations.  

 

If you say all shots are blurry around the edges, then I will take your word for it.  

 

Well, maybe that statement was a bit of an exaggeration on my part.  I'll admit to becoming a pixel peeper lately.  It's just kind of frustrating because I've seen the work of a few of my friends who are using this exact same lens for the same type of (RR) photography and their stuff is completely sharp throughout the frame and I wonder why quite a few of my shots aren't.  I know that cropping the soft/blurry edges is an option, but I try to avoid it doing so wherever possible.   

 

 Try taking shooting in One Shot mode, both with and without IS active.

 

I've taken 400-500 shots with this lens since I got it last summer.  I may need to just take it on a day trip and take 400-500 shots just in a single day at a variety of settings and see what works best.  Maybe it is something in my technique.

 

Heres another that I took last week, this time at the long end, with a 100% crop of the right side.  I noticed that for this one, I  had switched over to One-Shot AF.  Maybe it's just me, but the right side doesn't just look soft, it looks blurry.  Again, I understand that the extreme edge isn't going to be as sharp as the middle,  and it's on the edge of the DOF, but I think it could be much clearer.  All of the detail just seems to run together.  DPP_0080.JPGUntitled.jpgUntitled.jpg


 

Occasional Contributor
Posts: 13
Registered: ‎11-03-2016

Re: 18-135 Sharpness


Peter wrote:

You can use Live view and the focus box. Live view is slower but hasn´t any AF variance issues. Focus at something in the edges and upload a new picture.

 

I have never been a huge fan of live view except for video and the occasional indoor shot of the kids, , but to be fair, I've never really used it for my action photography.  I've always preferred the viewfinder, because I may only have a few seconds to get the composition where I want it when my subject is approaching at 50MPH.  

I also have a question for you. Where did you get your camera, because your firmware version is 5.5.9. It feels like a service firmware. Do you have a factory menu?

 

Funny you mention that.  Yes, when i purchased the camera (used) it did have factory firmware on it.  It has since been removed.  If you are interested in the back story, you can go back and see my user posts from a few months ago about the whole debacle.    


 

Esteemed Contributor
Posts: 2,781
Registered: ‎06-11-2013

Re: 18-135 Sharpness

I'm not certain what you used as your focus point.  The hyperfocal distance of a 35mm focal length at f/8 is about 27'.  If the camera focused on anything nearer then that would explain the issue.

 

Also, a lens doesn't necessarily have a "flat" focal plane.  It's typically just slightly curved and a bit closer at the corners than it is in the center (although lens designers do try to compensate for this to create a nearly flat field.)

 

I'd be interested in knowing how those tree leaves in left edge of frame look as well as a how the center looks (it'd be easier to judge this using the original out-of-the-camera image.)

 

If you look at the meridonal performance at f/8 for your lens at the 'wide' end (visit this page and click the "more" link at the end of the description to expand the page to show the full description, sample images, and MTF test curves) you'll see that the lens does have quite a noticeable fall-off in it's ability to resolve fine detail at the edges and corners of the frame (in other words, some loss of detail resolving is normal.)

 

There are other factors that can certainly come into play such as camera motion of a hand-held camera.  But your shutter speed was 1/640th at a 35mm focal length -- which is extremely good (you should have no difficulty hand holding a 35mm at 1/640th ... even if the lens didn't have image stabilization).  So I doubt that's the issue (I suppose you could blur it with motion, but you'd almost have to be trying to move the camera while taking the shot.)

 

BTW, the blur I see seems to be along the radial direction (from center point radiating to the outer edges and corners).  Such a blur would cause a poor score on the MTF curve for the "meridonal" direction.  On the Canon MTF curve, you'd want to look at the blue dashed lines.  There are two such lines... one thick, the other thin.  The thicker line shows performance using the thicker/bolder test lines (with larger gaps between lines) on an MTF test chart.  The thinner lines shows the performance using the finer lines (with narrower gaps) on the test chart.  Basically the finer line shows how the lines can resolve finer levels of detail.

 

See this page for an explantion:  http://learn.usa.canon.com/resources/articles/2013/reading_MTF_charts.shtml

 

The left edge of the graph shows lens performance in the very center of the lens (center axis of the image).  As you move to the right side of the graph, it's showing the perfrmance some number of millimeters away from the center point (as measured on the camera sensor).   An APS-C sensor camera has a diagonal measure of roughly 28mm... so the corner would be 14mm from center.   The far right side of the graph shows the performance of the lens in the extreme corners.

 

The vertical direction measures quality at that distance.  If the line is above the 0.6 mark then the lens is doing fairly good.  If it's above the 0.8 mark then it's extremely good.  If it's below the 0.6 level then it's fair to poor.  

 

I can't tell if you have the "STM" version of this lens... that's the better version.  The non-STM lens is extremely poor in the coenrs.

 

The non-STM version of the lens is good to about 7mm from center axis before it's ability to resolve fine detail drops out of the "good" category and into the "fair".  At 10mm from center it really takes a nose-dive into the poor/marginal category.

 

The STM version does quite a bit better (but still not good enough to compete with Canon's top end lenses).  The STM lens makes it to about 10mm from center axis before it drops out of the "good" category and while it does get into the "fair" category around the edges, at least it avoids the "poor" category (e.g. below 0.4 one graph).

 

You do have to be careful when staring at MTF charts.  First... they don't translate well across completely different types of lenses.  Second... lenses that can provide coverage for full-frame cameras have MTF charts where the horizonal axis is tested out to about 22mm from center axis (whereas an APS-C sensor camera using EF-S lenses only uses about the first 14mm... so if you were wondering how an EF 70-200mm f/2.8L IS USM II would perform on your camera, you would ignore everything past the 14mm point because your sensor isn't large enough to capture anything beyond that point.)

 

Also... MTF charts only provide insight into one particular attribute of a lens... and there are so many.  Sometimes a lens that doesn't have what you'd think of as a fantastic looking MTF curve... produces gorgeous-looking images that are hard to beat.  So it's not all about the MTF curve. 

 

You might be wondering... how DO photographers get staggering corner-to-corner sharpness (maybe you've seen such an image.)  These are often made by "stitching" images together.  Divide the image into a grid and the center area of each image can be used to provide the detail for that grid-square.   That's one technique (and there are others.)

 

Tim Campbell
5D II, 5D III, 60Da
Esteemed Contributor
Posts: 4,191
Registered: ‎08-13-2015

Re: 18-135 Sharpness

GenXRailmedia,

I am surprised to hear you say that you were 100 feet from the engine in the original shot you posted.  At a 35mm focal length, it looks more like 2 car lengths or less, or somewhat less than 50 feet, possibly close to 30 feet.  A distance of 100 feet is pretty far.  A basketball court is 90 feet.  Baseball bases are 90 feet apart.  Do you think that you were farther away than that?

 

How sharp is the front of the train, or wherever the focus point was established?  You will get your best results on most shots by using One Shot mode, and using the center AF point.  

 

What is the full model number of your lens?  The STM version of the lens is pretty good, but sharpness does fall off.  I still think most of your issue is related to depth of field.  These photos are not very good for evaluation as "test shots".  There are images that you can download and printout to use as test shots.  But, I have used the lines of a large empty parking lot to test super telephoto lenses.  The lines that define parking spaces are evenly spaced, and at known distances apart.

 

I think your lens is operating properly.  It is human nature to reject that which we do not understand.  But, it is quite possible that you are more likely seeing the limits of your photography skills, than the limits of your gear.  Your evidence that your lens is not performing well, raises more questions than resolving them.

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